In a typical semiconductor fabrication process, integrated circuits are formed on semiconductor substrates using a number of different processing techniques to create the transistors, resistors, capacitors, interconnects, and the various other circuit elements of a semiconductor device. In some processes, portions of the circuit which are designed for a specific functionality are formed separately on a die, and the die is then mounted on a packaging substrate and is used to impart that functionality to a host device. The die circuitry is typically accessed from bond pads formed on the final metal layer of the die. Hence, the bond pads provide a means for the transfer of electrical signals and power from and to the die via bonding wires, conductive bumps, and other elements of the conductive pathway formed between the die and the packaging substrate. The packaging substrate, in turn, provides electrical connections between the die and other circuit elements.
FIG. 1 depicts one example of a conventional wire bond packaged semiconductor device 51. As seen therein, the device 51 comprises a BGA packaging substrate 53 upon which is mounted a semiconductor die 55. A plurality of solder balls 57 are mounted on one face of the packaging substrate 53 to enable connection thereof to a host device. The die 55 is mounted to the opposing face of the packaging substrate 53 by way of a die attach adhesive 59.
The die 55 is equipped with a row of wire-bond pads 61 disposed along an edge 80 of its upper surface. In some implementations, the row of wire bond pads 61 may form a bond pad ring around the perimeter of the upper surface of die 55. The wire-bond pads 61 on the semiconductor die 55 are electrically connected to wire-bond posts 67 on the packaging substrate via bond wires 68. Each individual wire bond pad 61, and its associated wire bond post 67 and bond wire 68, may provide power, ground, or Input/Output (I/O) signal coupling between the die 55 and the packaging substrate 53. An adhesive fillet 76 is provided to further secure the die 55 to the packaging substrate 53. In some cases, the adhesive fillet 76 may be formed of the same material as the die attach adhesive 59. Though not shown, a molding material may be applied to complete the structure. The molding material will typically encapsulate the die and bond wires.
It will be appreciated from the foregoing that a device of the type depicted in FIG. 1 will have many signal bond pads, and will also have many power and ground wires connected to bond pads of those types. In particular, the device 51 shown therein is equipped with several bond wires 68 that contact bond pads 61 around the periphery of the die 55. An I/O cell is associated with each bond pad 61. In a typical implementation of such a device, there will also be bond pads associated with power and ground cells that form a ring around the outer perimeter of the die. Hence, there will be bond wires connecting bond posts 67 in the packaged substrate 53 to all of those pad types.